Like others who have already posted that they have multiple types and brands of thread, I want to keep them separate, but still waste time digging for the right bobbin I filled last week or last year. When I have to match thread colors, I often reach for the serger thread. I bought a pkg. of pipe cleaners at the dollar store, ran one through the cone and slipped the bobbin on before twisting the ends together. My serger thread lives in a big plastic tote box, no organization there, just dig. For the aurifil or connecting threads that I usually use for piecing, a snack size ziploc bag to keep thread and bobbin together works for now.
The hard plastic bobbin storage boxes tend to fly out of my hands and get cracked, chipped, or have a tiny plastic hinge broken off. A quilting magazine had a short tip on using golf tees to store thread spools and bobbins together. They failed to mention that the tees are a loose fit and tend to fly out of the spool. That means three items now to crawl around on the floor looking for. Amazon is still trying to sell me golfing equipment because I bought those tees. At a meeting, a door prize goodie bag included something that looked like big pink hairpins, intended to be shoved into the spindle hole on a spool of thread. Tension holds it together, but I don't know what you call them.